The invention relates to a drive unit for adjustment devices in motor vehicles with an electric motor, gearing and an electronic control device.
U.S. Pat. No. 5,272,938 describes a drive unit which has an electric disc rotor motor, and a gearbox formed as a reduction gearing, as well as a control device fed from a direct current voltage source wherein the housing of the disc rotor motor encloses the rotor disc, tablet-shaped permanent magnets and carbon brushes adjoining the rotor disc. Reduction gearing in the form of planetary gearing is integrated in an outwardly directed indentation of one of the two crankcase casings. An outer housing connected to the rotor of the disc rotor motor covers the housing of the disc rotor motor, the reduction gearing and a clutch so that the motor housing which encloses the electric motor is mounted inside the gearbox housing surrounding the gearbox thereby forming the housing of the drive unit.
The one crankcase casing of the motor housing receives a part of the reduction gearing and thus provides an additional mechanical function of the gearing but it also separates the electric disc rotor motor from the reduction gearing, but lined up with a double function of the one crankcase casing of the electric motor.
Through the double function of the one crankcase casing of the electric motor it is possible to make the drive unit particularly flat so that it can consequently be used as a hub drive for a cycle, but apart from the double function of the one crankcase casing of the electric motor only the common drive shaft is provided as one structural unit which is used both for the disc rotor motor and for the reduction gearing.
A drive unit with a reduction gearbox is described in DE 197 08 310A and is termed “harmonic drive gearing” and is located inside a rigid support ring which has a cylindrical internally toothed supporting area and an externally toothed radially flexible rolling bush. The rolling bush is elliptically deformed through a suitable drive device which consists inter alia of a planetary wheel unit mounted inside the rolling bush and having a sun wheel mounted on a drive shaft and driven by same, whereby the teeth of two planetary wheels engage in the external toothing of the sun wheel at two opposite places. The internal and external toothing differ by one tooth or several teeth. The toothed rim of the radially flexible rolling bush is pressed by the elliptically formed inner core of the drive unit into the cylindrical internally toothed supporting face of the rigid support ring.
As a result of the different number of teeth in the supporting surface and rolling bush a permanently continuous off-set stagger is produced between the interengaging circumferential sections so that one complete revolution of the drive shaft only causes the rolling bush to move on by the proposed difference between the number of teeth in the support ring and rolling bush. A very high reduction can thereby be achieved with a harmonic drive gearing of this kind.
DE 28 31 774 C2 describes an electric motor having a disc rotor in whose flat air gap an iron-free stator winding is mounted which is associated at least on one side with a permanently magnetized ring with axially magnetized segments and on both sides with soft magnetic flat discs for the magnetic short circuit. An electrodynamic tachogenerator is mounted coaxial with the rotor shaft so that the most compact unit possible is produced for the electric motor and tachogenerator.
The known unit of electric motor and tachogenerator consists of coaxial function elements of the electric motor and tachogenerator arranged in a row side by side wherein each unit is fully capable of functioning per se when the individual function elements are separated from each other.